Automatically controlled mixing plant



Feb. 18, 1941." E. A. PRATT 2,232,404

AUTOMATICALLY CONTROLLED MIXING PLANT Original Filed March 31, 1934 6Sheets-Sheet 1 Q N R WIT/(5S8: E d B /f Feb. 18, 1941. PRATT 2,232,404

' AUTOMATICALLY CONTROLLED MIXING PLANT Original Filed March 31, 1934 6Sheets-Sheet 2 FIG. 2.

Feb. 18,. 1941.

E. A. PRATT 2,232,404

AUTOMATICALLY CONTROLLED MIXING PLANT Original Filed March 31, 1934 6Sheets-Sheet 3 Feb. 18, 1941 E. A. PRATT I AUTOMATICALLY CONTROLLEDMIXING PLANT 6 Sheets-Sheet 4 Original Filed March 31, I934AUTOIA'I'ICALLY CONTROLLED MIXING PLANT Original Filed March 31, 1934 6Sheets-Sheet 5 96 Wren r01? [WW/65: f/muiza VII I III 6 Sheets-Sheet 6NR 35km Mv toxin E/A. PRATT Original Filed March 31, 1934 a RBRR NV\kuwkkau AUTOMATICALLY CONTROLLED MIXING PLANT Ale/NJ Feb. 18, 1941.

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Patented Feb. 18, 1941 UNITED STATES PATENT OFFICE Edmund A. Pratt,Devon, Pa., assignor to Barber Asphalt Corporation, Barber, N. J., acorporation of New Jersey Continuation of application Serial No.718,522, March 31, 1934. This application July 13, 1938,

Serial No. 2 1 9,986

17 Claims.

This invention relates to a mixing plant or other processing plant whichrequires that'ingredients be fed in predetermined proportions and whichis automatically controlled either totally or partially and isparticularly adapted for the preparation of paving mixtures.

This application is a continuation of my application Serial No. 718,522,filed March 31, 1934.

In the preparation of mixtures having more than two or three ingredientswhich must be added in well defined quantities, it is diiilcult toprovide proper manual control in such fashion as to prepare a batch in acomparatively short period, since so many matters need be taken intoaccount and proper sequential addition of ingredients to a mixer orother processing equipment insured. Thi is particularly true it a numberof operators are controlling the ingredients and something occurs in theaddition of any one of them. Too much or too little of an ingredient maybe added, or the addition may not occur at the proper times with theresult that spoiling of batches may possibly occur.

The broad object of the present invention is to provide means forautomatically controlling the proportioning of the ingredients of themixture, the introduction of ingredients into a mixer or otherprocessing equipment in the desired .sequence, the discharge of thefinished mixture from the mixer after a definite and predeterminedamount of processing, and particularly.

.by means of specific tests automatically performed to prevent anymixture being made which does not contain the predetermined quantitlesof each of the several ingredients or which has not received thepredetermined amount of processing, neither more nor less. The inventionis particularly applicable to the formation of paving mixtures in thepreparation of some of which considerable care must be exercised toobtain the desired results.

More specifically, the invention applies to an asphalt mixing plantwhich comprises-a mechanical mixer in which the ingredients of anasphalt pavement are mixed together, weighing boxes in which theingredients are weighed out preparatory to their being introduced intothe mixer, hoppers from which the ingredients are intermittently ted tothe weighing boxes as required, elevators or other means for raising theingredients from the ground to the hoppers, and a source 01 power, and,if desired, when the asphalt is red to the mixer in a pulverized orgranulated state, a mechanical pulverizer. Such mixing plant constitutesthe specific embodiment of the invention which is described herein. Moredetailed object of the invention relate to the provision of means asindicated above in which proper control of ingredients is efiected andwhich is of a flexible nature so that the timin of events occurring inthe operation may be adjusted.

Further objects of the invention will become apparent from the followingdescription read in conjunction with the accompanying drawings, inwhich:

Fig. l is a diagrammatic elevation showing the various parts of atypical mixing plant embodying the invention;

Fig. 2 is a diagrammatic view showing the controls associated withdelivering means for a granular material such as sand or stone;

Fig. 3 is an elevation illustrating the association of various controldevices for different ingredients;

Figs. 4, 5 and 6 are sections through controlling mechanism taken asindicated at 4-4, 5-5, and 6-6, respectively, in Fig. 2;

Fig. 7 is a conventionalized wiring diagram corresponding to that ofFig. 2 but simplified by the omission of power supplies, etc. so as toindicate more clearly the interaction of the various electricalelements; I

Fig. 8 is a diagrammatic view similar to Fig. 2 but showing thecontrolling means for a liquid ingredient;

Fig. 9 is a somewhat similar diagrammatic view showing the controls foremptying the ingredient mixer; and

Fig. 10 is a diagram indicating the operations of the various parts intheir relationships to each other.

The invention may be best understood by initial reference to a singleingredient unit together with its associated controls. The arrangementof such unit is illustrated in Fig. 2, to which reference will first bemade.

The mixer forthe various ingredients is indicated at 2, this mixerincluding stirring elements of conventional character, for example,involving blades mounted upon one or more shafts designed to either stirthe mixture without imparting to it an advancing movement, or to botheffect stirring and advance of the ingredients to better accomplishmixing. The mixer 2 is supplied with the ingredients from varioussources, as will be brought out in greater detail hereafter. One of thedirect sources of a solid ingredient to the mixer is the weighing box 4,whose outlet is controlled by means of a gate 6 pivoted about ahorizontal axis 8 and normally urged towards closed position by theweight l8. The specific mechanisms whereby this gate is controlled willbe described in detail later.

The weighing box is supplied with a solid ingredient by a belt i 2driven through suitable reduction gearing by a motor l4, the beltreceiving the supply of ingredient from a hopper l6 located above it.The discharge end of this hopper is such in its relationship to the beltthat when a certain amount of material is located on in turn connectedby a link 26 to a beam 28- fulcrumed on a support indicated at 38. Thebeam 28 carries a counterpoise 32 which may be moved along its lengthand held in adjusted position in conventional fashion. Downward movementof the right-hand end of the beam 28 is limited by a stop 34. Restingupon the righthand end of the beam 28 is a roller carried by a dependingprojection 36 from an upper beam 38 which is also fulcrumed on thesupport indicated at 38 and carries a counterpoise indicated at 48.Upper and lower stops, respectively, indicated at 42 and 44, limit themovements of the beam 38 and are so placed that neither of them isengaged when the beam is in its horizontal balancin position. While onearrangement of weighing means has been disclosed, it is obvious thatthis may take various forms well Q'known to the art.

The beam 28 is provided with a mercury switch indicated at 46 and soplaced that when the beam 28 is above its horizontal position, themercury within the switch will join the contacts 85 therein to close acircuit. The beam 88 is provided with three mercury switches 48, 58 and52. The first of these, 48, is so arranged that it will close itscircuit when the beam 88 is in its horizontal balancing position orbelow such position, that is, up to and when a. predetermined weight ofcontents exists in the weighing box 4. The switches 58 and 52 are soarranged that when the beam 38 is below its balancing position beyond apredetermined tolerance, the switch 58 will be closed, and when the beamis above its balancing position beyond a predetermined tolerance, theswitch 58 will be opened and the switch 52 closed. In other words, oneor the other of switches 58 and 52 will be closed whenver the beam isabove or below the predetermined tolerance. The control by means ofthese switches will be brought out in greater detail hereafter.

- Secured to the weighing box 4 is a gate operating solenoid 54 which isarranged to attract downwardly an armature 56 link-connected with alever 58, which is pivoted concentrically with the gate 6. A spring 68normally urges the lever 58 counterclockwise as viewed in Fig. 2 so asto withdraw the plunger 58 from the solenoid 54.

The spring at the same time urges the lever against a stop 62 carried bythe gate. When the plunger is attracted by the solenoid, the lever 58 isrocked clockwise into engagement with a stop 64 carried by the gate andafter such engagement by its continued movement is adapted to open thegate positively if the contents of the weighing box do not initiate suchopening. To prevent the contents from opening the gate, however, untilthe desired time, there is provided a latching arrangement involving thelatching member 66 pivoted upon the gate. A spring 68 urges this latchin a clockwise direction to its limiting position in engagement with thestop 64. The left-hand end of the latch 66 is provided with a camsurface engageable by the lower end of the lever 58 to rock the latch ina counterclockwise direction to release it from engagement with the lug18 secured to the weighing box. By reason of the arrangement Justdescribed, it will be seen that the contents of the weighing box areineflfective to open the gate until, by the attraction by the solenoid54 of its armature 56, the lever 58 is rocked to cam the latch member 86to a position where it disengages the lug Ill. The gate is thenpositively opened by the further attraction of the plunger 56 throughthe engagement of lever 58 with the stop 64. This power actuation of thegate insures that it remains open until discharge is completed.

When the latch 66 is in its latching position, its end causes engagementof contacts I2 by reason of its pressing the upper spring-held one ofthe pair. When the plunger 56 of the solenoid 54 is in its lowerattracted position, it engages the movable one of a pair of contacts I4,opening the circuit in which these contacts are interposed. Thefunctions of both of the switches just mentioned will be brought outlater.

A plurality of controlling devices for the various ingredients aredriven from a common source indicated as a shaft 16, which desirably isslowly driven through suitable reduction gearing from the same source ofpower as the mixing elements in the mixer 2.

The shaft 16 carries the fixed element 18 of a clutch, the movableelement 88 of which is splined to a shaft 8i and is urged intoengagement with the member I8 by a spring 82 A forked lever 84 isconnected at one end to a collar carried by the clutch element 88 and atits other end to a plunger 86 adapted to be attracted by a solenoid 88so as to cause a disengagement of the clutch elements and consequentstoppage of the various controlling mechanisms. The shaft 8i carries agear 88 which, through an intermediate idler arrangement illustrated at82, drives another idler 84, which forms one of a set of intermediateidlers meshing with gears 86 as indicated in Fig. 3.

As will be obvious hereinafter, the length of time of a cycle ofoperation may be adjusted by changing the relative sizes of the gears 88and 82. Each of the gears 88 except one directly drives the controllingmechanism for the devices handling a single ingredient. The excepted onedrives a similar controlling mechanism of the type indicated in Fig. 9for determining the time of discharge of the mixed ingredients from themixer. In the present instance, there are six controlling mechanisms totake care of the five ingredients and the mixer.

One of the controlling mechanisms is specifically illustrated as drivenby the gear 88 shown in Fig. 2. The gear 86 is mounted upon a shaft 88to which is secured a flanged head indicated shaft 98 is a sleeve I02which, at its righthand end, carries a flange I04 arranged to flatwiseengage the flange I and provided with an indicating marking, forexample, in the nature of a line inscribed on its periphery which may bebrought into proper relationship with respect to the markings on I00.Journalled upon the sleeve I02 is a second sleeve I06 which similarlycarries a flange I08 also provided with a marking, which may be lined upwith the markings on I00. Adjustment of the controlling mechanism iseffected by the relative rotation of the sleeves I02 and I06 withrespect to the shaft 08 and their fixation in such adjusted position bymeans of a clamp IIO, which serves to tightly hold the flanges togetherwhen the screw member H2 is tightened. As will be evident hereafter,each of the other controlling mechanism is similarly arranged and forproper operation all oi them are relatively adjusted to secure a propertiming of events.

The sleeve I06 carries an arm II4 which supports an outer roller adaptedto engage a cam II6 carried by the carrier IIO, which is secured to ashaft I20 mounted to turn freely in the supporting frame for thecontrolling mechanism. The carrier II8 supports a mercury switch I22.Depressions I 26 in the edge of the carrier may selectively receive theend of a spring detent I24 so as to yieldably hold the carrier either inthe clockwise position illustrated in Fig. 6, in which the switch isopen, or in an alternative counterclockwise position, in which theswitch is closed.

Mounted loosely upon the shaft I20 there is an element I28 which isconnected by means of a spiral spring I34 with a collar I35 secured tothe shaft I20. The element I28 is provided with a cam portion I30engageable by an actuating roller carried by an arm I 32 secured to asleeve I02.

The arms H4 and I32 are so related as to successively efi'ect a rockingof the carrier II8 to close and then open the mercury switch I22. Thearm II4 engages the cam II6, rocking it counterclockwise as viewed inFig. 6 to cause the right hand depression I26 to pass beneath the detentI24. The switch is then closed. Thereafter the arm I32 engages theelement I28, rocking it clockwise and thereby tensioning the spring I34to cause it to rock the shaft I20 clockwise and thereby move the switchI22 to its open position. The spring connection is provided to preventbreakage in case the arms I I4 and I32 should he accidentally set so asto act simultaneously upon the cams H6 and I30. This, of course, shouldnot occur in operation butthe actions should be successive as Justindicated and as will be described in greater detail later.

Contacts I38, I42 and I46 are provided arranged to be closed byengagement with arms I36, I40 and I44, respectively. The first of thesearms is carried by the sleeve I02 while the latter two are carried bythe sleeve I06. All of the arms already described may be adjusted uponthe sleeves so as to set them in properly timed relationships to eachother. The arrangement of the arm I40 with respect to the contacts I42is illustrated specifically in Fig. 4. The other arms and contacts areof similar construction.

In addition to the controlling elements already described, eachingredient unit has some or all of certain other elements. Among theseis the starting relay I48 for the motor I4. Additional relays I50, I52,I54, I56, and I58 are provided for eifepting various operations. Therelay I50 is arranged to close the circuit through a solenoid I60, whichattracts the plunger I62 against the tension of a spring I66. Thecircuit to the solenoid I60 is periodically interrupted by a comm-utator I68 so that the plunger I62 is successively attracted andreleased to cause its head I64 to hammer the bottom of the weighing box4 to insure liberation of any materials which may tend to stick therein.The source of power for the operation of the majority of the elements inFig. 2 is indicated conventionally at I10, while batteries are indicatedin local relay circuits. The batteries have been illustrated to avoidcomplication, it being understood, of course, that in the practicalarrangement of the device only a single source of power would beemployed for actuating all of the electrical devices. In Fig. '7, therehas been conventionalized the wiring diagram to illustrate in a betterfashion the control of the various electrical elements by others. Inthis diagram, all types of switches, including mercury switches, areconventionalized as knife switches, which in certain instances are thearmatures of relays. Both power solenoids and relay coils areillustrated as simple coils. Sources of power have been omitted, itbeing understood that each of the circuits would be provided withsuitable power from a common source or a plurality of sources.

From Fig. 7 a general understanding of the interlocking of the elementsmay be had. It will be noted that the solenoid 88 serving for thedisengagement of the main driving clutch of the control mechanisms iscontrolled, by three separate relays I54, I56, and I58 of each of theunits containing all three or of one relay at least of a unit which doesnot contain all three. Energization of each of these relays of thevarious units represents an abnormal condition and will result in adisengagement of the clutch member 80 and stopping of all of the controlmechanisms.

The relay I54 is in series with the mercury switch 46 and the contactsI38 and is also in series with the relay I50 which serves to close thecircuit through the solenoid I60, which circuit also contains theinterrupter I68. In practice, of course, the relays I50 and I54 may beincorporated into a single unit.

The relay I56 is in series with the contacts I 42 and also with theparallel arrangement of the mercury switches 50 and 52.

The relay I58 is in series with the contacts I46 and the contacts I4which are controlled by the energization of the solenoid 54 if suchenergization is effective to attract the plunger 56. The solenoid 54 iscont-rolled by the relay I52, which is in turn controlled by the mercuryswitch I22. Additionally, the solenoid 54 is effective to open thecontacts "I2 through the liberation of the latch 66, which contacts I2,together with the mercury switch 48, are in series with the relay I48which controls the circuit of the motor I4.

The above description of Fig. 7 outlines briefly the relationships ofthe various electrical elements. The control of a solid ingredient inFig. 2 has been first specifically described, since it involves all ofthe elements necessary for proper control of any ingredient, including,for example, the means for hammering upon the weighing box to insuredischarge. It also includes all of the elements which are essential forcontrolling the discharge from the mixer. Consequently, a considerationof Figs. 2 and 7 will include the most elaborate type of operation ofany of the units. Before proceeding to a discussion of the handling ofliquid ingredients or the discharge from the mixer, the sequence ofoperations occurring in the action of the unit of Fig. 2 will bedescribed with reference to Fig. 10. This figure, taken together withFigs. 2 and '7, will illustrate the detailed operations involved.

' Fig. 10 is merely diagrammatic and while the abscissae represent timeintervals, there has been no attempt made to indicate the relativelengths of these intervals, but only their sequence, and to that extentthe figure is very substantially distorted, since relatively longintervals may occur in the introduction of the materials into theweighing boxes or tanks, the discharge therefrom, and the mixing ascompared with the in-' tervals in which tests of proper operations aremade. Furthermore, the two periods designated as indicating the deliveryof preceding and subsequent ingredients would be very large if theingredients are to be added successively rather than simultaneously.

Various characteristic elements are indicated at the left of Fig. 10. Ingeneral, the rise of a line corresponding. to one of these elementsindicates the energization of a solenoid, relay, or motor, or closure ofswitches or contacts. The lowermost of the graphs illustrates by itsrise the increase of contents of the weighing box.

As soon as the gate 6 is closed following a previous delivery ofcontents from the weighing box, the contacts I2 will be closed as wellas the as mercury switch 48 so that the motor I4 will be H the weighingbox 4 is empty, the beam 38 will rest upon its lower stop 44 while thebeam 28 will be in its horizontally balanced position floating above itsstop 34, but not in contact with projection 36, in such position thatthe switch 46 will be open. This condition corresponding to the tareweight of the weighing box 4 is secured by adjustment of thecounterpoise 32. The counterpoise 40 will be located in position corre-,sponding to the desired weight of material to be discharged into themixer for a batch. This adjustment will be such that when the weighingbox contains the predetermined quantity of material, the beam 38 willoccupy a horizontal balanced position.

As soon as a very small quantity of material has been introduced intothe weighing box, the beam 28 will rise until it engages the rollercarried by the downward projection 36. It will, of course, not raise thebeam 38 but the motion at this time is sufficient to close the switch46. No

immediate action, however, is effected by such closure, since thecontacts I38 remain open.

As the material enters the weighing box 4, the force exerted tending toraise the right-hand end of the beam 38 increases. As soon as theminimum permissible weight is exceeded, the beam 38 will rock upwardlyto an extent causing an opening of the switches 48 and 50.

These switches 48 and 50 may be combined into one controlling a circuitcontaining relays which in turn would control separate circuits. Theyare shown separate in the present disclosure for simplicity. Under someconditions, as for example where the flow of material does not cease fora quite appreciable time after the opening of switch 48, it may bedesirableto have the switch 48 open before switch 50 to avoid an excessflow of material such as might exceed the upper limit of weightcontrolled by switch 52. The switch 48 is in series with the relay I48which controls the operation of the motor I4. Consequently, if theoperation has occurred correctly, the feed of material by the belt I2will cease and the weight of material within the box 4 will be betweenthe limits of tolerance. Under proper conditions, the beam will not haverisen sufliciently to cause a closure of the switch 52. Following thisevent, a test is made to determine whether the weight is within thelimits of tolerance due to proper operation. The arm I40 closes thecontacts I42 as indicated in the diagram of FignlO. An abnormalcondition of either the switch 58 or the switch 52 is indicated in Fig.10 in dotted lines. If, when the switch I42 is closed, both the switches58 and 52 are open, the relay I56 will not operate and the solenoid 88remains deenergized and consequently the clutch member 88 remains indriving engagement with the clutch member 18. If, however, either switch50 or 52 is closed due to a deviation 7 from proper weight exceeding thetolerances, then the relay I56 will be energized, energizing thesolenoid 88 and disengaging the clutch, stopping the machine.Preferably, the reason for the stoppage is indicated by audible orvisual means, for example, the use of lamps, which are indicated invarious circuits in Fig. 2.

If stopping of the apparatus occurs at this time, the cause may betraced and the condition rectified by either a further manual additionof material to the weighing box or removal of material therefrom. Afterrectification of the condition, switches 50 and 52 will both be openedand operation will proceed. Immediately after operation continues, thecontact at I42 is broken.

The next event consists of the closure of mercury switch I22 by theaction of the arm H4. The closure of this switch energizes the relay I52which in turn energizes the solenoid 54. If conditions are proper, theplunger 56 will be attracted, opening the gate and opening the contactsat 12 and I4, initiating a discharge of the material.

At this point, however, there is a possibility of failure of operation;for example, the gate may be jammed so as not to open under the pull ofthe solenoid 54. In this event, the switch I4 will not open. This lastswitch will be opened only when the solenoid is moved to a sufficientextent to open the gate 6.

If the gate is opened, the discharge of the material should begin andthe beam 38 should immediately drop, closing both switches 48 and 50. Ifthe gate is sufliciently opened, there is, of course, no question of thefact that sufiicient material will leave the weighing box to cause suchdropping of the beam, so no test need be made to determine whether ornot the beam is dropped. However, a test is made to determine whetherswitch I4 has been opened. This test is made by the closure of thecontact I46. If the switch 14 is not opened, the relay I58 will beenergized, causing energization of the solenoid 88 and a disengagementof the clutch, stopping the mechanism. The abnormal conditions will beevident from the dotted linesin Fig. 10, the normal conditions in thisfigure being represented by full lines.

After any abnormal condition occurring at this time is rectified, thematerial should flow from the weighing box so as to empty it to such extent that the switch 46 will be opened. If, howpreventing operation ofthe motor I4.

ever, an amount of residual material remains in the weighing boxexceeding a predetermined tolerance, the switch 46 will not be opened.The abnormal conditions then arising are made the subject; of a testwhich depends upon the closure of the contacts I38. From Fig. '1, itwill be seen that if 46 is closed, then when I38 closes the relay I54will be energized, causing the solenoid 88 to disengage the clutch. Atthe same time, the relay I58 is energized, causing the periodicenergization of the solenoid I68 to operate the hammer to tap theweighing box. If the material is dislodged by the action of the hammer,the abnormal condition is automatically cured, since, as soon as thematerial leaves the weighing box, the switch 46 will be opened andoperation resumed. If, however, the action of the hammer is insufficientto remove the residual material, then manual correction of the conditionmust be made.

Following the removal of the material from the weighing box, the switchI22 is rocked to its opened position; the relay I52 and solenoid 54 arethen deenergized. The release of the gate thus effected should result inits being moved to closed position under the action of the weight I8, soas to cause a closure of the contacts 14 and 12. If, however, the latch86 does not properly engage the lug 10 so as to lock the gate in closedposition due either to a failure of the gate to completely close or to afailure of the latch to drop over the lug, then the contacts 12 willremain disengaged, preventing the closure of the circuit of the relayI48 and consequently The abnormal condition thus resulting may be eithernoted immediately or, as specifically illustrated, it will come to theattention of an attendant, inasmuch as when a weight test is made in thenext cycle, it will be found that the weight of the weighing box isdeficient, since, of course, it will be empty. The operation would thenbe automatically stopped until the gate was completely closed.

It has been pointed out above that Fig. 10 is not intended to representthe relative times during which the operations take place. During theabove described operation of a cycle for a single solid ingredient,other solid and liquid ingredients will have been added. In the cyclesinvolving other additions, any abnormal conditions will likewiseenergize the solenoid 88, stopping the operation of the mechanism. Thevarious events involved in the delivery of any one ingredient arenecessarily timed by a proper setting of the sleeves I02 and I06relative to the shaft 98 corresponding to that ingredient. If successivedelivery of ingredients to the mixer is desired, then relativeadjustments of the sleeves on any one shaft must be made with respect tothe sleeves on all of the other shafts. Of course, the time of dischargeof the mixer must be so adjusted. It will be obvious, however, that thevarious operations can overlap to such extent as will produce asatisfactory operation. The use of a sinple controlling solenoid 88insures that the events cannot happen out of a proper order, since thecontrolling mechanism of all of the units will be definitely stopped.

While certain conditions were heretofore described as abnormal, thestoppage of the controlling mechanism may very well occur in normaloperation. If, for example, the delivery of an ingredient to a weighingbox is relatively slow, then the test to determine whether a full weighthas been reached may occur before that full weight is normally reached.The controlling mechanism, however, will then be restarted as soon asthe full weight is reached. While the various tests have beenconsiderably stressed, it must not be assumed that the abnormalconditions which they represent will ordinarily occur. The tests merelyrepresent checks which are made for the sake of absolutely insuring theproduction of proper mixtures.

Having described fully the operation involved in the addition of asingle ingredient, the operations in connection with the addition of aliquid ingredient and the emptying of the mixer will be readilyunderstood. Since both of these involve quite substantial duplication ofcontrolling elements, the description will not be repeated in detail butthere will be referred to only the elements which differ from thosealready described and do not correspond to those already described.

Considering first Fig. 8, which illustrates the apparatus associatedwith the delivery of a liquid ingredient, such as an oil or the like, asupply tank I12 is provided which is arranged to deliver the ingredientthrough a conduit I14 which is controlled by a valve I16 adapted to beactuated by a solenoid I18. The valve I16 corresponds to the conveyor I2and its operating solenoid I18 corresponds to the motor I4. The solenoidI18 is controlled by the relay I90 which corresponds to the relay I48.

Discharge from the weighing tank is effected through a conduit I82 whichis controlled by a valve I84 arranged to be opened by the energizationof a solenoid I86. The plunger of the solenoid is adapted to open thecontacts I92. As soon as opening of the valve begins, the contacts I88are disconnected. The solenoid I86 is energized through a relay I93which is in turn energized by a mercury switch corresponding to I22. Thecounterparts of the elements just mentioned will be readily apparentupon reference to Fig. 2, *from which it will be seen that I84corresponds to gate 6, I86 corresponds to 54, I92 to 14 and I88 to 12.These various elements correspond identically in their functions, thevarious switches insuring stopping of the operation in case the valveI84 is not opened or closed at the proper times.

Relays I94, I96 and I98 correspond to I54, I56 and I58, respectively.The elements of the controlling mechanism need not be fully described,since their functions are identical with those used in the othermechanism. The solenoid 88 is, of course, the same one as that shown inFig. 2.

The control of the delivery of the mixer involves a considerablesimplification of the controlling elements as compared with thoseinvolved in the handling of ingredients inasmuch as no weighing ormeasuring is involved. The simplification, however, consists primarilyin the omission of various elements and will, therefore, be clear from abrief consideration of Fig. 9 in conjunction with what has already beendescribed.

The outlet of the mixer 2 is controlled by a sliding gate 288 which isconnected with a piston 284 sliding in a cylinder 206 into the ends ofwhich compressed air or other fluid may be introduced through thepassages 208 connected to the controlling valve 2III which, by rockingin opposite directions, alternately connects the conduits 288 to thesupply of working fluid through 2l2 or with the atmosphere or dischargetank through 2|4. The valve 2l0 is controlled by a solenoid 2|6 actingin opposition to a spring 218. The solenoid 2H5 corresponds to thesolenoid 54 and is controlled by a relay 220 corresponding to I52, therelay 220 being energized by a mercury switch corresponding to I22. Thepiston rod 202 connected to the gate 200 carries a collar 203, which isarranged to hold contacts 226 open when the gate 200 is closed and whichis arranged to disengage contacts 222 when the gate is fully opened. Thecontacts 226 are in the circuit of a relay 228 which is in turn incircuit with the contacts 229 which may be engaged by an arm 23L If, atthe time contacts 229 are engaged, the contacts 226 are also engaged byreason of the fact that the gate is not fully closed, then the relay 228will be energized to stop the operation. The test by the action of arm23! on contacts 229 would, of course. occur after the gate wassupposedly closed and before any ingredients were delivered to themixer.

The contacts 222 are disconnected only when the gate is fully opened;consequently, if the arm 225 closes the contacts 221 before the gate isfully opened, the relay 224 will be energized, stopping the operation byenergizing the solenoid 88.

It will be clear from the above that the automatic mixing of variousingredients may be accomplished with complete assurance that the properproportions are introduced into the mixer.

The diagrammatic illustration of the assembly of the parts is indicatedin Fig. 1. The hopper I6 is indicated therein as supplied with solidingredients by means of an elevator 260. A similar hopper 254 locatedadjacent to it is supplied from another elevator indicated at 262, anddelivers its solid ingredient upon a belt 256 similar to belt [2, whichin turn delivers into a Weighing box 258. Another solid ingredient issupplied from a hopper 248 by means of a belt 250 and is introduced intoa weighing box 252. The ingredient handled by 248 may possibly be acomparatively fine dust and arrangements are therefore made to preventloss by suitable housing. A crusher or pulverizer 236 may be provideddriven through a belt 234 by a source of power such as an electricmotor, a steam engine, or preferably an internal combustion engine 230.The material crushed or pulverized by this apparatus is deliveredthrough a pipe 238 to a container 240 in which it is separated fromcarrying air and is then fed by a belt 242 to a weighing box 244. Theinternal combustion engine may be arranged to drive the mixer throughsuitable reduction gearing indicated at 246. The belts which are shownare merely conventionalized conveyors since others may be used, eithermotor driven, or driven by the engine through electrically controlledclutches. Alternatively gravity feed may be employed, control being bythe the use of gates or valves.

The liquid-containing tank I12 may be jacketed if it contains, forexample, a viscous bituminous material, or in case a steam or internalcombustion engine is used as the source of power, the jacket may be soarranged as to be heated by the exhaust from the engine led to itthrough a passage 232. The delivery conduit IT4, which has already beendescribed and which may also be jacketed to insure free flow, isarranged to lead the fluid contents to the weighing tank I which rectlyinto a suitable truck when the apparatus is used for the preparation ofpaving mixtures. This truck may then be taken directly to the locationwhere paving is being done.

The gate of the mixer has been described as operated by a fluid. This isdesirable if the fluid used is made available for some other purposes.If not, the gate may be otherwise controlled. It will be obvious thatthe details of operation may be subject to considerable variation. Ingeneral, it may be desirable to provide for the cutting out of theautomatic controls for various ingredients so that these ingredients maybe added under manual control. Likewise, provision may be made fortotally cutting out of the operation those elements associated with oneor more ingredients. This may be accomplished by not only stopping thefeed of that ingredient, but making inoperative its associated mechanismfor controlling the clutch 80. It may also be desirable to add, in theformation of a single batch, some particular ingredient at spacedintervals. This may, of course, be effected merely by a duplication ofthe control elements for that ingredients so that its particular cyclewill occur two or more times in a complete 0 cycle of operation.

The relative timing may, of course, be effected merely by the properadjustments of the arms and sleeves forming parts of the controllingmechanisms. cycle may be changed merely by varying the speed of rotationof the shafts 98 by gear changes as described above. For example, thismay be desirable if especially prolonged mixing is desired. It

will be noted that in the modification described, 5

as soon as one ingredient is delivered to the mixer a new batch of thatingredient is weighed so as to be ready for delivery at the propersubsequent time. Suitable provision may be made to stop the mechanism atthe end of a complete cycle, although in general, particularly whenpaving mixtures are being prepared, the cycles may be automaticallyrepeated.

It may be pointed out that the automatic control mechanism functionsentirely independently of the manner in which the ingredients are fed tothe weighing boxes. The weighing boxes could be filled by hand withoutaltering the tests as to accuracy of weight, and without any effectwhatever upon the control principle. In other words. the tests areeifective irrespective of whether or not there is automatic delivery andweighing.

While the apparatus has been rather broadly described, its particularadvantages in connection with the preparation of paving mixtures may nowbe pointed out. There are known, for example, paving mixtures which areformed without the use of heat, the paving being produced from coldmixtures. Such mixtures may include as ingredients crushed stone,emulsified flux, sand, filler dust and hard asphalt. The emulsified fluxreferred to may comprise a bituminous material cut back by an oil andsuitably d spersed in order to form an emulsion. This emulsion may bemixed with the crushed stone, sand and filler dust and with a pulverizedhard asphalt. By the breaking of the emulsion the asphalt particles arefluxed and caused to coalesce and provide a mixture which, after beinglaid and pressed down.

will form a suitable paving. The emulsified flux may be, in someinstances, replaced by a flux comprising bituminous material liquefiedbythe addition of oil.

In the preparation of a mix such as indicated above, the ingredientsmust be used in their The total time taken for a complete properproportions and in proper sequence. The plant indicated in Fig. 1 isvery well adapted for this purpose and is representative of thearrangement of elements for the preparation of paving mixes. The variousingredients are added to the mixer from the supplies indicated in thatfigure. The hoppers I6, 254 and 248 may contain, respectively, stone,sand, and the filler dust. An emulsified flux may be supplied from thetank I12 which, in such case, need not be heated. If, on the other hand,the flux consists only of bituminous material of suitable consistency,then the jacket may be used to maintain it in a proper liquid condition.The asphalt. is supplied in lumps to the pulverizer 236, where it isfinely crushed and delivered by a blower through the conduit 238 intothe receptacle 240. It is found that the harder grades of asphalt atleast may be pulverized and then retained for substantial periodswithout coalescing. The rearrangement of the apparatus to effect thiswill be obvious; such rearrangement does not substantially change thecontrols.

The various additions of materials may be either successive orsimultaneous, followed by a prolonged mixing period, or may overlap toany extent that may be desired. The total cycle length is, of course,very much reduced by the fact that the filling of the weighing boxes orweighing tank may occur during the additions of other ingredients or themixing. It will, of course, be obvious that more or less ingredients maybe added depending upon the character of the character of the productdesired. If it is necessary to keep the product hot, then the mixer maybe jacketed and heated by steam or exhaust gases, or other means knownto the art.

Although for descriptive purposes the plant has been described abovewith reference to particular types of mixes, it may be pointed out thatit is actually designed to be used for practically all known types ofbituminous mixtures Whether they involve hot or cold aggregates, hotasphalt, emulsified asphalt, pulverized asphalt, hot or cold flux, oremulsified flux, the change required in any case being only those whichwould be obvious to one skilled in the art from reading thepresentspecification.

In fact, the plant is of even greater utility in the preparation of hotmixes than in the preparation of cold mixes since accurate proportioningof the type obtainable in accordance with this invention is ofparticular importance in the case of the former. The discussion of usein cold mixes is therefore to be understood as in no way restrictive ofthe scope of the invention. For example, the apparatus is applicable tothe preparation of a paving mix in which the stone may be coated with asoft bitumen and subsequently mixed with dust and a hard bitumen. Itwill be obvious that such mixes require only obvious modifications ofthe apparatus for their production. It may also be pointed out that itis broadly applicable to many other chemical or physical processes.

It will be clear that numerous changes may be made in the specificembodlment of the invention Without departing from its scope as definedin the for the occurrence of a normal condition in the series' ofoperations automatically effective irrespective of the occurrence ofsaid normal condition and only following a substantial interval of timeafter such condition should have occurred; and means rendered operativeby said testing means at the termination of said interval of time tointerrupt said series of operations automatically in the event that suchnormal condition has not occurred.

2. In combination, means arranged to effect, in a normally sequentialseries of operations, accumulation and measurement of a predeterminedquantity of material, said means including a container, a closuretherefor, means for delivering material to the container, and means forindicating the amount of material in the container; auxiliary means fortesting for the occurrence of normal conditions in the series ofoperations, said normal conditions including an empty condition of thecontainer prior to delivery of material thereto, and a finalpredetermined quantity of material therein, said auxiliary means beingeffective irrespective of the occurrence of any of said normalconditions and only following a substantial interval of time after eachcondition for which a test is made should have occurred; and meansrendered operative by said testing means at the termination of suchinterval of time to interrupt said series of operations automatically inthe event that such normal condition has not occurred.

in a normally sequential series of operations,

accumulation, measurement and delivery of a predetermined quantity ofmaterial, said means including a container, a closure therefor, meansfor delivering material to the container, and means for indicating theamount of material in the container; auxiliary means for testing for theoccurrence of normal conditions in the series of operations, said normalconditions including an empty condition of the container prior todelivery of material thereto, a final predetermined quantity of materialtherein, and opening of said closure to discharge said material, saidauxiliary means being effective irrespective of the occurrence of any ofsaid normal conditions and only following a substantial interval of timeafter each conditionfor which a test is made should have occurred; andmeans rendered operative by said testing means at the termination ofsuch interval of time to interrupt said series of operationsautomatically in the event that such normal condition has not occurred.

4. In combination, measuring means; means controlling discharge of thematerial from the measuring means; means for effecting a test todetermine whether the quantity of material in the measuring means liesbetween given upper and lower limits and eifective only following asubstantial interval of time after the quantity of material in themeasuring means should lie between said limits; and means controlled bysaid testing means to initiate and eiTect discharge from the measuringmeans only in the event that the quantity of material in the measuringmeans lies between said limits.

5. In combination, measuring means; means controlling delivery ofmaterial to the measuring means; means controlling discharge of thematerial from the measuring means; means for automatically interruptingsaid controlled delivcry of material to the measuring means; means foreffecting a test to determine whether the quantity of material in themeasuring means lies between given upper and lower limits and effectiveonly following a substantial interval of time after interruption ofdelivery of material to the measuring means; and means controlled bysaid testing means to initiate and effect discharge from the measuringmeans only in the event that the quantity of material in the measuringmeans lies between said limits.

6. In combination, measuring means; means controlling delivery ofmaterial to the measuring means; means controlling discharge of thematerial from the measuring means; means for automatically interruptingsaid controlled delivery of material to the measuring means; and meansautomatically operative only in the event that the quantity of materialin the measuring means lies between predetermined limits after asubstantial interval of time following interruption of the delivery ofmaterial, to initiate and eifect discharge of the material from themeasuring means.

7. Means for effecting the delivery of a plurality of ingredients inpredetermined amounts to a common receptacle including a plurality ofmeasuring means; means for efl'ecting automatic delivery of materials tothe measuring means; and means automatically operative only in the eventthat the quantity of material in each measuring means lies betweenpredetermined limits after a substantial interval of time followinginterruption of delivery of material thereto, to initiate and effect itsdischarge and subsequent discharges from the various measuring means inpredetermined timed relationships.

8. Means for effecting the delivery of a plurality of ingredients inpredetermined amounts to a common'receptacle including a plurality ofmeasuring means; means for effecting automatic delivery of materials tothe measuring means; and means for initiating and effecting successivedischarges from the various measuring means in predetermined timedrelationships, said means being automatically operative to effectdischarge of any measuring means only in the event that operation; meanscontrolled by said timing means for effecting discharge of the materialfrom the measuring means at predetermined intervals; and meanscontrolled by the measuring means for stopping the operation of thetiming means if any discharge is not properly effected.

10. Means for effecting the delivery of a plurality of ingredients inpredetermined amounts to a common receptacle including a plurality ofmeasuring means; timing means normally continuously operating; means foreffecting automatic delivery of materials to the. measuring means, meanscontrolled by the timing means for effecting successive discharges ofthe materials from said various measuring means into the receptacle inpredetermined time relationships, and means for stopping the operationof the timing means if, by the time discharge from any of said measuringmeans is to be effected the quantity of material therein does not liebetween predetermined upper and lower limits.

11. In combination, weight measuring means comprising a receptacle;means for supplying material to the receptacle; means for automaticallytesting the tare weight of the receptacle prior, to operation of thesupplying means; and means automatically preventing operation of thesupplying means if the tare weight is abnormal and for automaticallytiming the initiation of operation of the supplying means if the tareweight is normal.

12. In combination, means arranged to effect, in a series of operations,measurement of a predetermined quantity of material and discharge ofsuch quantity; controlling means for the operations; actuating means fornormally continuously driving the controlling means; and means operativeto automatically interrupt the operation of the actuating means upon theoccurrence of an abnormal condition in the series of operations and tocontinue the operation of the actuating means when such abnormalcondition is corrected.

13. In combination, means arranged to effect, in a. normally sequentialseries of operations, accumulation and measurement of a predeterminedquantity of material; controlling means for the operations; actuatingmeans for normally continuously driving the controlling means; means fortesting for the occurrence of a normal condition in the series ofoperations only following a substantial interval of time after suchcondition should have occurred; and means rendered operative by saidtesting means at the termination of said interval of time to interruptthe operation of the actuating means in the event that such normalcondition has not occurred.

14. In combination, means arranged to effect, in a normally sequentialseries of operations, accumulation and measurement of a predeterminedquantity of material; controlling means for the operations; actuatingmeans for normally continuously driving the controlling means; and meansoperative to automatically interrupt the operation of the actuatingmeans upon the occurrence of an abnormal condition in theseries ofoperations and to continue the operation of the actuating means whensuch abnormal condition is corrected.

15. In combination, measuring means arranged for the accumulation of apredetermined quantity of material; means for interrupting furtherintroduction of material into the measuring means after the measuringmeans contains substantially said predetermined amount of material;means for effecting discharge of material from themeasuring means; andmeans for preventing discharge of material from the measuring means fora substantial period following the action of said interrupting means,and thereafter for preventing normal discharge of material from themeasuring means if the quantity of material in the measuring means doesnot lie within pre determined upper and lower limits.

16. In combination, measuring means; means controlling delivery ofmaterial to the measuring means; means automatically operative after apredetermined quantity of material is in the measuring means forinterrupting delivery of material to the measuring means; and means fornormally periodically effecting discharge from the measuring means atpredetermined approximately equal time intervals after and if themeasuring means contains a quantity of material lying withinpredetermined upper and lower limits; said last named means being timedto effect discharge independently of the time of the filling operation.

17. In combination, measuring means; means controlling delivery ofmaterial to the measuring means; means automatically operative forinterrupting delivery of material to the measuring means after aquantity of material exceeding a predetermined minimum is therein; meansincluding a timing means for automatically effecting discharge ofmaterial from the measuring means only after a substantial intervalfollowing the interruption of. delivery of material to the measuringmeans; and means for automatically preventing the operation of saidmeans for automatically effecting discharge if the quantity of materialin the measuring means is outside predetermined limits.

EDMUND A. PRATT.

